1. Field of the Invention
The present invention relates to a polymer dispersion type liquid crystal display element useful as, for example, a TV or flat panel display device.
2. Description of the Related Art
Recently, a polymer dispersion type liquid crystal display element attracts attentions as a new type liquid crystal display element. The new type liquid crystal display element, which was disclosed for the first time in Published Unexamined Japanese Patent Application No. 61-83519, is constructed such that a film prepared by dispersing a liquid crystal material in a polymer matrix material is held between a pair of electrodes.
In the polymer dispersion type liquid crystal display element, the liquid crystal material dispersed in the polymer matrix material differs in the refractive index from the polymer matrix material, when an electric field is not applied across the film held between the two electrodes. As a result, scattering of light is brought about so as to make the film opaque. When an electric field is applied across the film by applying voltage between the two electrodes, the liquid crystal molecules dispersed in the polymer matrix material are oriented, with the result that the refractive index of the oriented portion of the liquid crystal is made substantially equal to that of the polymer matrix material. It follows that the film is made transparent.
The polymer dispersion type liquid crystal display element, which utilizes the particular operation principle described above, makes it unnecessary to use a polarizer, an orientation film, etc., which are required in the conventional TN type liquid crystal display element used in, for example, a miniature TV receiver. It follows that it is possible to markedly simplify the manufacturing process of the polymer dispersion type liquid crystal display element. In the conventional polymer dispersion type liquid crystal display element, however, the polymer matrix material has a relatively high resistivity, leading to requirement of a high driving voltage. Also, the conventional liquid crystal display element of this type is low in its response speed. Further, the light shuttering function is performed by the scattering of light, leading to a low contrast.